Drying apparatus for papermaking

ABSTRACT

A web-drying apparatus having a hood enclosing two parallel transverse rows of drying cylinders set one above the other at a considerable distance from each other, each web run between the upper and lower rows of drying cylinders being lined on either side with a vertical row of jet boxes each of which has a convex profile along the side facing the web and which alternate in position with the jet boxes in the opposite row, so that the web will be dried on the drying cylinders and also as it runs in a wavy path from one row of drying cylinders to the next, while the web is exposed to a hot blast from the convex side of each jet box on both sides of the web, but without touching the jet boxes.

United States Patent [1 1 3,634,948 Kobayashi [4 1 Jan. 18, 1972 [54] DRYING APPARATUS FOR PAPERMAKING Primary ExaminerCarroll B. Dority, Jr.

Attorn Geor eB. Ou'evolk 72 Inventor: Tadashi Kobayashi, 1560-2 l-ligashihara, ey g 1 Tenma, Fuji-shi, Shizuoka-ken, Japan [57] ABSTRACT [22] Filed: 1970 A web-drying apparatus having a hood enclosing two parallel [21] Appl. No.: 65,538 transverse rows of drying cylinders set one above the other at a considerable distance from each other, each web run between the upper and lower rows of drying cylinders being [52] US. (ii ..34/l566,b22g/37 lined on either side with a vertical row of jet boxes each of [51] if; C which has a convex profile along the side facing the web and [58] ie d o are 4/ which alternate in position with the jet boxes in the opposite row, so that the web will be dried on the drying cylinders and [56] References Cited also as it runs in a wavy path from one row of drying cylinders UNITED STATES PATENTS to the next, while the web is exposed to a hot blast from the 954 D 1 34/156 convex side of each et box on both sides of the web, but 2,689,196 9 ame s without touching the jet boxes 3,216,638 I 1/1965 Brickle et al.. 34/156 X 3,485,429 12/1969 l-lutzenlaub ..226/97 3 Claims, 4 Drawing Figures 8 iv I) I l l I l l I 6a\ 6 /'l\ 60 t l? "fl) (fi -'1"):( i -"Y1 (:l .'f 411-": n? W W in H; 4 r-\" \..l3i "rr -J Li r1 rwx '4LJIf-T I .l L /r": I l .l I: H ii 2 :l P um r' 4i.4;", T'\:\'L.J: ei r 3 EBLi-m r- .i I I I i I i I i i r \L r1:\+\ i3 ha r": IF J Li /I": 'F'\:\:L.4|4 i .l"r14r\ 4' LJ I'nr' r l :1 g 5 l} 1:

3 e a ti te I, I I, 7 I (I i i i 1 II I I I H I I l 2/ 2 PATENTEDJUHBHYZ 3.634.948

sum 3 0F 3 INVENTOR ATTORNEY DRYING APPARATUS FOR PAPERMAKING BACKGROUND OF THE INVENTION BRIEF DESCRIPTION OF THE PRIOR ART Heretofore, the art has endeavored to accomplish such web drying by means of a drier as illustrated in FIG. 4 in the accompanying drawings, in which two parallel transverse rows of upper and lower drying cylinders 20 and 21 are installed close to each other, with the individual cylinders in each row arranged at regular intervals in positions alternating with those in the other row. The web P to be dried shuttles back and forth between the two rows, running from the first cylinder in one row to the first cylinder in the other row to the second cylinder in the first row and so on. The web is pressed on each row of cylinders by a separate canvas belt 22 or 23, which wraps the web around each cylinder in each row. While being dried, therefor, the web is not free to expand or shrink, and often subjected to such severe drying that it tends to be curled, swollen, wrinkled, pinked or flulTed on the surface. MOreover, moisture is normally present between the web P and the canvas belt 22 or 23 where they meet or part on the cylinders in the upper and lower rows 20 and 21, with the result that the two edges of the web tend to dry faster than the middle. This uneven drying often causes the web to develop irregularities in surface luster or waviness on the takeup roll.

In addition, the conventional type of drier requires a large elongated space for installation since it consists of drying cylinders arranged in transverse rows, and the factory space above the upper and lower rows which are installed close to each other is usually wasted. Recently, however, papermaking speeds are becoming higher and higher, and if these rapid papermaking machines are to be used with driers of the conventional type, they will need vast installation areas, which are increasingly difficult to obtain in the industry today.

OBJECT OF THE INVENTION It is an object of the present invention to provide a drying apparatus for papermaking which helps to increase the tear strength of the web being produced.

Another object of the present invention is to provide a drying apparatus for papermaking capable of drying the web uniformly in the widthwise direction.

The invention also contemplates providing a drying apparatus for papermaking with an improved drying capacity.

It is also the purpose of the invention to provide a drying apparatus for papermaking which can be installed in a limited space and which can be adapted to high papermaking speeds.

SUMMARY OF THE INVENTION With the foregoing and other objectives in view, the invention comprises a web drying apparatus having a hood enclosing two parallel transverse rows of drying cylinders set one above the other at a considerable distance from each other, each web run between the upper and lower rows of drying cylinders being lined on either side with a vertical row of jet boxes each of which has a convex profile along the side facing the web and which alternate in position with the jet boxes in the opposite row, so that the web will be dried on the drying cylinders and also as it runs in a wavy path from one row of drying cylinders to the next while the web is exposed to a hot blast from the convex side of each jet box on both side of the web, but without touching the jet boxes.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents a preferred embodiment of the present invention, showing said embodiment in front elevation;

FIG. 2 is a side elevation of the embodiment represented in FIG. 1;

FIG. 3 illustrates the arrangement of jet boxes used in the embodiment of FIG. 1; and,

FIG. 4 represents a section of the prior art type of drier in front elevation.

DETAILED DESCRIPTION In the drawings illustrating the preferred embodiment of the invention, numeral I refers to an upper row of drying cylinders, which are arranged transversely at regular intervals.

Below the upper cylinder row 1, running parallel therewith at a considerable vertical distance therefrom, thereis a lower row of drying cylinders 2, which are arranged at regular intervals and alternate in position transversely with respect to the drying cylinders of the upper row.

Jet boxes 3 each have a convex face 4, in which there are numerous perforations 5 for jetting a hot blast.

Between said upper and lower rows of drying cylinders l and 2, a number of said jet boxes 3 are arranged in pairs of vertical rows, in each pair of rows of jet boxes the convex faces 4 of the boxes confront each other. A wet web of paper P shuttling between the upper and lower rows of drying cylinders l and 2 is routed between each pair of rows of jet boxes 3 via upper and lower guide rolls 6a-6b and 7a7b, respectively.

A closed hood 8 encloses all of said upper and lower drying cylinders l and 2 and all of said jet boxes 4. The web P is introduced into the closed hood 8 from one end thereof via a roll 9, and the dried web is led out of the hood 8 via guide rolls 10 and 11. I

Each of said jet boxes 4 has a hot air inlet 12, and the closed hood 8 is equipped with hot air outlet ducts I3 and 14, which lead to fans 15 and 16, respectively. To said inlets 12, hot air is supplied from the fans I5 and 16 through air ducts l7 and I8, and then through a common air duct 19.

OPERATION OF THE INVENTION How the present invention works is now explained in conjunction with said preferred embodiment. The web P is routed via the guide roll 9, around the first drying cylinder 2 in the lower row, via the guide roll 7a, up between the first pair of vertical rows of jet boxes 3, via the guide roll 6a, around the first drying cylinder I in the upper row, via the guide roll 6b, down between the second pair of vertical rows of jet boxes 3, via the guide roll 6b, down between the second pair of vertical rows of jet boxes 3, via the guide roll 7b, around the second drying cylinder 2 in the lower row, and so on, thus shuttling between the upper and lower rows of drying cylinders and running through one pair of vertical rows of jet boxes after another. 7

With the web P running in the manner described above, hot air from a hot air source (not shown) provided inside the closed hood 8 is fed by the fans 15 and 16 into the jet boxes 3, from which said hot air is blown through the perforations 5 onto the surfaces of the web P, causing it to wave as it runs vertically. The effect of these hot blasts combine with that of the upper and lower drying cylinder 1 and 2 to dry and web P.

In the above example, an apparatus embodying the present invention is used independently. Such an apparatus, however, may also be inserted in a conventional drying arrangement essentially consisting of drying cylinders only, preferably in the part of the process where the web is most liable to shrink.

The present invention eliminates the various disadvantages of the conventional drier mentioned above. The web, running in a wavy manner under the effect of the hot blasts, is free to shrink, and therefore acquires greater tear strength and better uniformity of strength in the widthwise direction.

As each hot blast hits the web uniformly over the entire width thereof, no drying irregularities occur in the widthwise direction. Consequently, the web is free of irregularities in luster, and does not become wavy on the takeup reel.

The hot blasts blown direct onto the surfaces of the web at close range combine with the upper and lower drying cylinders to dry the web more efficiently then the conventional drier does. Having more time to dry, moreover, the web has less tendency to develop such faults as curling, swelling, wrinkling, surface picking, and fluffing.

The vertical arrangement ofthe jet boxes permits a saving in plant floor space, and the space thus saved may be used to install more drying equipment. The present invention, therefore, makes it possible to adapt the drying part of a papermaking process to higher papermaking speeds without any additional plant floor space required therefor.

Although the present invention has been described in conjunction with a preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

lclaim:

l. A drying apparatus for papermaking, comprising a closed hood, two parallel upper and lower horizontal rows of drying cylinders installed therein one above the other at a considerable vertical distance from each other, the drying cylinders in each of said upper and lower horizontal rows being arranged transversely at regular intervals in positions alternating with those of the drying cylinders in the other horizontal row defining vertical web travel paths between said horizontal rows so that a wet web to be dried may be routed from one drying cylinder in one horizontal row to the next drying cylinder in the other horizontal row, thus shuttling between said upper and lower horizontal rows along said travel paths, and pairs of vertical rows of jet boxes lining said travel paths between said upper and lower horizontal rows of drying cylinders, the jet boxes in each of said paired vertical rows being offset one from the other alternating vertically with those in the other vertical row, and each ofsaid jet boxes having a convex profile vertically along the side thereof that faces the web travel paths, said convex profile at one row being nested in the corresponding convex profile of the other row and disposed to blow a hot blast onto a web passing along said travel path from each of said jet boxes causing said web to run in a wavy course form one row of drying cylinders to the other, said hot blasts and said drying cylinders thus combining to dry said web.

2. A drying apparatus for papermaking as claimed in claim 1, wherein the web to be dried is routed from one transverse row of drying cylinders to the other via a guide roll installed between each upper drying cylinder and the top of each pair of vertical rows of jet boxes below said upper drying cylinder and via a guide roll installed between each lower drying cylinder and the bottom of each pair of vertical rows of jet boxes above said lower drying cylinder.

3. A drying apparatus for papermaking as claimed in claim 1, wherein said hood has wet and dry ends and at the wet end of the hood the web is first routed around the first drying cylinder in the lower row and goes up, whereas at the dry end the web travels downward between the last pair of vertical rows ofjet boxes, at the end of which said web is led out of said hood. 

1. A drying apparatus for papermaking, comprising a closed hood, two parallel upper and lower horizontal rows of drying cylinders installed therein one above the other at a considerable vertical distance from each other, the drying cylinders in each of said upper and lower horizontal rows being arranged transversely at regular intervals in positions alternating with those of the drying cylinders in the other horizontal row defining vertical web travel paths between said horizontal rows so that a wet web to be dried may be routed from one drying cylinder in one horizontal row to the next drying cylinder in the other horizontal row, thus shuttling between said upper and lower horizontal rows along said travel paths, and pairs of vertical rows of jet boxes lining said travel paths between said upper and lower horizontal rows of drying cylinders, the jet boxes in each of said paired vertical rows being offset one from the other alternating vertically with those in the other vertical row, and each of said jet boxes having a convex profile vertically along the side thereof that faces the web travel paths, said convex profile at one row being nested in the corresponding convex profile of the other row and disposed to blow a hot blast onto a web passing along said travel path from each of said jet boxes causing said web to run in a wavy course form one row of drying cylinders to the other, said hot blasts and said drying cylinders thus combining to dry said web.
 2. A drying apparatus for papermaking as claimed in claim 1, wherein the web to be dried is routed from one transverse row of drying cylinders to the other via a guide roll installed between each upper drying cylinder and the top of each pair of vertical rows of jet boxes below said upper drying cylinder and via a guide roll installed between each lower drying cylinder and the bottom of each paiR of vertical rows of jet boxes above said lower drying cylinder.
 3. A drying apparatus for papermaking as claimed in claim 1, wherein said hood has wet and dry ends and at the wet end of the hood the web is first routed around the first drying cylinder in the lower row and goes up, whereas at the dry end the web travels downward between the last pair of vertical rows of jet boxes, at the end of which said web is led out of said hood. 